%---------------------------------------------------------------%
%------ 2) Plotting the mag and phase response of the  ---------%
%------    Karplus-Strong Filter with a 300Hz signal   ---------%
%---------------------------------------------------------------%

fs = 44100;
fo = 300; 
L = fs/fo-0.5;
delta = L-floor(L);         % gives us the fractional delay. =0.5
L = floor(L);               % gives us the integer delay. =146
a = (1-delta)/(1+delta);
L_delay = zeros(1,L-2);     % allows us to use a sample delay of L
R = 0.999;                  % R is the gain, must be less than 1
B = [(a/2), (a/2+1/2), 1/2, L_delay];
A = [1, a, L_delay, (-a/2*R^L), -(a/2*R^L+1/2*R^L), (-0.5*R^L)];
[H, W] = freqz(B, A, 1024);     % B is the num and A is the den of H(z)
W = (W*fs)/(2*pi);

figure();
subplot(2,1,1);
plot(W, abs(H));
title('Magnitude Response of Karplus-Strong (300Hz)');
xlabel('Frequency (Hz)');
ylabel('Amplitude');

subplot(2,1,2);
plot(W, angle(H));
title('Phase Response of Karplus-Strong (300Hz)');
xlabel('Frequency (Hz)');
ylabel('Amplitude');

%---------------------------------------------------------------%
%---- 4) Filtering and plotting an impulse through the KS  -----%
%---------------------------------------------------------------%

impulse = [1, zeros(1, 3*fs)];         % 1 is the impulse followed by many
KS_impulse = ksfilter(fo,fs,impulse);  % zeros so we can hear the effects
sound(KS_impulse,fs);                  % of the KS filter

ts = 1/fs;
t = 0:ts:3;                             

figure();
plot(t, KS_impulse);
axis([0 3 -1.1 1.1]); 
title('An impulse modeled by the KS filter');
xlabel('Time (s)');
ylabel('Amplitude');
wavwrite(KS_impulse,fs,'Lab6-Impulse_Response');

%---------------------------------------------------------------%
%---- 5) Filtering and plotting noise through the KS  ----------%
%---------------------------------------------------------------%
                                  
noise = 2*rand(1,(0.01*fs)+1)-1;                % The noise burst lasts
noise = [noise, zeros(1,(3*fs)-(0.01*fs))];     % for a very short time
KS_noise = ksfilter(fo,fs,noise);               % Again followed by zeros
sound(KS_noise,fs);
                                    
figure();
plot(t, KS_noise);
axis([0 3 -1.1 1.1]);              
title('A noise burst modeled by the KS filter');
xlabel('Time (s)');
ylabel('Amplitude');
wavwrite(KS_impulse,fs,'Lab6-Noise_Burst');